(a) Field of the Invention
The present invention relates to a reader antenna and an RFID electronic shelf including the same, and more particularly, to a reader antenna capable of simultaneously recognizing many individual items (item level tagging), and an RFID electronic shelf including the same.
(b) Description of the Related Art
The application field of radio frequency identification (RFID) in the ultra-high frequency (UHF) band has been extending from case or box unit recognition to individual item recognition as it has been recently used for an RFID electronic shelf.
The material and shape of items to be mounted on an RFID electronic shelf, the shape of a packaging material, the method of displaying items, and so on may be diversified according to application fields. Thus, a reader antenna for an RFID electronic shelf is emerging as one of the methods for simultaneously recognizing a plurality of items displayed on the RFID electronic shelf.
Recently, active research has been conducted on RFID electronic shelf applications in the field of RFID technology in the high frequency (HF) band and the field of RFID technology in the ultra-high frequency (UHF) band. The RFID technology of the HF band employing magnetic coupling is being studied in the RFID electronic shelf field, placing stress on excellent field characteristics for liquids and metals compared to the UHF band, but the recognition rate is drastically degraded due to interference between RFID tags, interference between tags and readers, and the like. The UHF band RFID technology using backscattering of electromagnetic waves, having advantages in that it has a relatively long recognition distance and similar field characteristics to those in the UHF band in a near field zone, is being studied in the RFID electronic shelf field. However, there is still a problem of recognition rate degradation due to a fading zone, caused by a change made to items to be displayed and a display method, and a polarization mismatch caused by the direction of tags to be displayed. Particularly, a conventional fixed reader antenna is directly applied to an electronic shelf in most cases because little research has been conducted regarding a reader antenna for an RFID electronic shelf in the UHF band. This leads to poor mountability of the reader antenna on the shelf.
Moreover, some reader antennas being studied for RFID electronic shelf applications in the UHF band cannot solve the problem of misrecognition caused by a polarization mismatch with tags, and a fading zone.
That is, in order to simultaneously recognize a plurality of tags in an item display environment where a plurality of items having different physical properties and shapes may be arbitrarily displayed on an RFID electronic shelf, the reader antenna for the RFID electronic shelf has to be easily mounted on the electronic shelf, and has to be capable of transmission and reception of polarization of arbitrary tags. Further, a technique of forming a near field on the RFID electronic shelf is required to avoid tag misrecognition caused by a fading zone. However, there are many difficulties in designing a reader antenna for an RFID electronic shelf having the above-mentioned characteristics by the conventional HF band antenna technology and the UHF band antenna technology.